Instrument flushing system

ABSTRACT

A medical instrument includes an instrument shaft with exit holes near a distal end of the shaft, a tool coupled to the distal end of the shaft, and a backend. The backend may include a mechanism that manipulates a drive element that extends through the shaft and couples to the tool, a fluid inlet, and a fluid channel assembly providing fluid communication between the fluid inlet and the proximal end of the shaft. Cleaning fluid is directed into the fluid inlet, through the fluid channel assembly, and into the shaft. A chassis or other structural piece of the backend may form part of the fluid channel assembly.

RELATED APPLICATION

This patent application claims priority to and the filing date benefitof U.S. Provisional Patent Application No. 62/362,386, entitled“INSTRUMENT FLUSHING SYSTEM” filed Jul. 14, 2016, which is incorporatedby reference herein in its entirety.

BACKGROUND

Minimally-invasive medical procedures often employ medical instrumentshaving a tool or end effector or other manipulation element at thedistal end of an elongated instrument shaft. During such a procedure,the distal end of such a medical instruments may be inserted throughsmall incisions and/or natural lumens to position the distal tools at awork site in a patient, and a surgeon or other medical personnel maycontrol the tools to perform desired clinical functions. The instrumentshafts are generally long and thin and may, for example, be over 50 cmin length and less than 1 cm in diameter. Despite the small diameters ofsome medical instruments, multiple tendons, push-pull elements, andpower or signal lines may extend through the length of the instrumentshaft.

Complex medical instruments are typically expensive, and users benefitif medical instruments can be reused for multiple procedures. Themedical instruments do, however, directly contact patients and must besterilize for reuse. Before being sterilized, the instrument generallymust be cleaned to remove any fluids, particulates, or othercontaminants that may have entered the instrument during a previousprocedure. Full disassembly of the medical instrument for such cleaningmay be impractical, and so systems and methods are needed for cleaningthe inside of an instrument shaft that do not require disassembling theinstrument.

One cleaning system for a medical instrument includes a flush tube,e.g., a thin walled, flexible, plastic tube that runs the length of theshaft of the medical instrument. The flush tube may particularly extendfrom a backend (proximal end) of the instrument to a distal end where atool attaches to the shaft. (In these medical instruments, the ends ofstructures closest to a robot or other control device are commonlyreferred to as the “proximal” ends, while the ends closest to the toolare commonly referred to as the “distal” ends.) The proximal end of theflush tube may be connected so that cleaning fluid (e.g., water) may befed through the flush tube to the distal end of the instrument shaftwhere the cleaning fluid exits the flush tube. The cleaning fluid fromthe flush tube hits a seal at the distal end of the instrument shaft andreturns back through the instrument shaft, and the returning fluid mayflush any contaminants through the inside of the shaft until thecleaning fluid washes contaminants out of the medical instrument throughgaps in a backend housing of the medical instrument. For this system,the flush tube must be carefully routed to prevent the flush tube frombecoming kinked, because a kink would block the flow of cleaning fluid.Also, the instrument shaft needs to have sufficient internal space forthe flush tube, for fluid return, and for any drive cables, drive rods,and electrically energized lines needed for the clinical function of themedical instrument. A medical instrument that provides a high degree offunctionality through a small diameter instrument shaft, e.g., aninstrument shaft with a diameter less than about 8 mm and particularlyhaving an instrument shaft with articulated joints, may not have spacefor a flush tube path that can reliably avoid kinking of the flush tube.

SUMMARY

In accordance with an aspect of the invention, a medical instrumentroutes cleaning fluid in a proximal-to-distal direction through aninstrument shaft without use of a flush tube extending though theinstrument shaft. Cleaning fluid may exit the instrument shaft thoughexit holes located near the distal end of the shaft. Joints, such aswrists, and other mechanism at the distal end of the instrument shaftmay be flushed using the proximal-to-distal flow or may be subject todirect cleaning through cleaning vents in the distal mechanisms.

One specific implementation of a medical instrument includes a shaftwith exit holes near a distal end of the shaft, a tool coupled to thedistal end of the shaft, and the backend including: a mechanism thatmanipulates a drive element that extends through the shaft and couplesto the tool; a fluid inlet; and a fluid channel assembly incommunication with the fluid inlet and containing the proximal end ofthe shaft.

Another specific embodiment is a method for cleaning a medicalinstrument. The method may include allowing the injection of a cleaningfluid into a fluid channel assembly, the fluid channel assemblycontaining a proximal end of a shaft of the medical instrument. A driveelement extends through the fluid channel assembly and through theshaft. The drive element couples to a tool at a distal end of the shaft.The method further includes removing contaminants from inside the shaftby allowing or guiding the cleaning fluid to flow through the shaft in aproximal-to-distal direction. The method further includes facilitatingthe draining of the cleaning fluid out of the shaft through to exitholes near the distal end of the shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B respectively show perspective and top views of anexample implementation of a medical instrument using proximal-to-distalflushing.

FIG. 2 shows an exploded view of a multi-piece chassis providing a fluidpath through an instrument backend into an instrument shaft in a medicalinstrument in accordance with an example implementation.

FIG. 3A shows a partial cutaway view of a flush path feeding a cleaningfluid through an instrument backend into an instrument shaft of amedical instrument in accordance with an example implementation.

FIG. 3B shows an exploded view illustrating a flush cap and a cableguide through which drive elements may enter an instrument shaft of themedical instrument of FIG. 3A.

FIG. 4A shows a bottom view of an example implementation of a cableguide.

FIG. 4B shows a bottom view of an example implementation of a flush cap.

FIG. 4C shows a bottom view of the cable guide of FIG. 4A being pressedagainst the underside of the flush cap of FIG. 4B to form openings thatseal around or closely fit drive cables.

FIG. 5A illustrates an example implementation of a cable guide havingconnectors for lines used to electrically shield an instrument shaft.

FIG. 5B shows the cable guide of FIG. 5A when the gable guide connectedto electrical shielding lines guides drive elements of a medicalinstrument.

FIG. 6A illustrates an example implementation of a cable guide havingopenings for lines used to electrically energize a tool at the distalend of an instrument shaft.

FIG. 6B shows the cable guide of FIG. 6A when the cable guide guidesdrive elements and electrical lines in a medical instrument.

The drawings illustrate examples for the purpose of explanation and arenot of the invention itself. Use of the same reference symbols indifferent figures indicates similar or identical items.

DETAILED DESCRIPTION

A system and method for cleaning a minimally invasive medical instrumentdirects a cleaning fluid into a proximal end of an instrument shaft sothat the cleaning fluid flows through the instrument shaft in aproximal-to-distal direction and exits the instrument shaft through oneor more exit holes at the distal end of the instrument shaft. A capsystem at the proximal end of the instrument shaft may provide a closefit (contact or near contact, although not necessarily sealing contact)to drive cables or rods so that a sufficient amount of cleaning fluidfed into a flush channel in the instrument chassis flows into theinstrument shaft. The exit holes may be located near the distal end ofthe solid portion of the instrument shaft. To maintain insufflationpressure during use of the medical instrument, to minimize contaminationentering the instrument shaft, and to provide the medical instrumentwith bending stiffness, strength, and lower cost, the exit holes may besmall and only provided near the distal end of the instrument shaft,while the proximal portion of the instrument shaft does not have holesthat might otherwise weaken the instrument shaft. A sheath, which may bedisposable, may be used to cover the holes during a medical procedure tofurther minimize insufflation loss and soiling. For convenience, aninput cleaning port may be located in the instrument housing of abackend of the medical instrument. A proximal portion of the cleaningsystem may particularly include a housing or chassis in which theinstrument shaft is mounted and which contains a channel or fluidconduit that directs fluid from an external inlet to the proximal end ofthe instrument shaft. A flush cap through which drive elements andelectrical lines may extend into the instrument shaft may cap a fluidtrough in the chassis or housing and may provide a close fit toactuation elements such as drive cables or rods.

Although the above examples and other discussions herein often refer tomedical procedures and medical instruments, the techniques disclosedalso apply to non-medical procedures and non-medical instruments.

FIG. 1A shows a perspective view of an example implementation of amedical instrument 100 in accordance with an example implementationusing a proximal-to-distal flush. Medical instrument 100 generallyincludes an end effector (also called a “tool”) 110 at a distal end ofan elongated instrument shaft 120 that extends from a backend 130.Distal tool 110 and instrument shaft 120 may have multiple degrees offreedom of movement relative to backend 130, and in the illustratedconfiguration of FIG. 1A, medical instrument 100 has six degrees offreedom corresponding to: two types of actuation of a first wrist orjoint 111; two more types of actuation of a second wrist or joint 112;opening or closing movement of jaws 113; and rotations of instrumentshaft 120 about its central or length axis. Other implementations ofmedical instruments may provide more, fewer, or different degrees offreedom of movement.

FIG. 1B shows a top view of instrument 100 and particularly illustratesan interface through which instrument 100 may engage and mount on arobotic system. In particular, as shown in FIG. 1B, backend 130 includessix input spindles 141 to 146 with external engagement features that maybe shaped and positioned to engage actuators in a docking port of arobotic system such as the da Vinci@ Surgical System commercialized byIntuitive Surgical, Inc. During a medical procedure, input spindles 141and 142 may engage first and second actuators, e.g., drive motors, inthe robot, so that the robot can rotate input spindles 141 and 142 topull drive cables extending to joint 111 and thereby control actuationof wrist or joint 111. Third and fourth actuators in the robot mayrotate input spindles 143 and 144 to pull drive cables extending towrist or joint 112 to thereby control actuation of wrist or joint 112. Afifth actuator may rotate input spindle 145 to push or pull a push-pullrod that extends to jaws 113 and controls opening or closing of jaws113, and a sixth actuator may rotate input spindle 146 to control rollrotation of instrument shaft 120.

In accordance with one aspect disclosed herein, backend 130 has a flushpath that directs cleaning fluid into a proximal end instrument shaft120 so that fluid flows and flushes around and along the drive elementsen route from the proximal end of instrument shaft 120 to exit holes 122as shown in FIG. 1A. Exit holes 122 in instrument shaft 120 may be neara distal end of a long fluid tight proximal portion of shaft 120. Inparticular, the proximal fluid tight portion of instrument shaft 120 maybe hole-free and therefore may be structurally stronger than if holeswhere provided along the full length of instrument shaft 120. In distaltool 110, tubular links 114 and 115 may also include holes 116 (alsocalled “vents 116”) through which cleaning fluid may be applied to driveelements or other structures in tubular links 114 and 115. The strengthof links 114 and 115 may be less critical in some medical systems, sincesuch links are close to the distal end of instrument 100 and thereforesupport shorter moment arms for external forces. Holes 116 may permittool 110 to be directly cleaned, e.g., by spraying cleaning fluid from aposition adjacent to distal tool 110. In some implementations, a seal124 may be provided between instrument shaft 120 and tool 110 and mayseal around the drive elements that extend through instrument shaft 120and into distal tool 110. Seal 124 may help maintain insufflationpressure, e.g., prevent distal-to-proximal air flows through holes 116and back through instrument shaft 120 when gas insufflation inflates awork site for a medical procedure. Seal 124 may also reduce or minimizethe entry of blood, particulates, or other contaminants into instrumentshaft 120.

FIG. 1A further shows how a housing of backend 130 may include an inlet150 into which water or other cleaning fluid may be injected duringcleaning of instrument 100. Inlet 150 may be sized and shaped to coupleto standard cleaning equipment and in one specific implementation mayinclude a Luer port fitting. The housing or chassis elements of backend130 may route cleaning fluid from inlet 150 into a proximal end ofinstrument shaft 120. FIG. 2, for example, is an exploded view showingpieces 210 and 220 that fit together to form a portion of a housing orchassis for a medical instrument such as instrument 100. In someembodiments, piece 210 comprises a part or all of the housing and may betermed a housing piece. In some embodiments, piece 220 comprises a partor all of the chassis and may be termed a chassis piece. Piece 210particularly includes a fluid channel from an inlet such as inlet 150FIG. 1A to a hollow protrusion 212, and pieces 210 and 220 fit togetherso that the inlet is in fluid communication though hollow protrusion 212with a fluid trough 222 in piece 220. In contrast to a separate tube asa fluid channel, structural pieces form the fluid channel.

Instrument shaft 120 is mounted in piece 220 so that a proximal end ofinstrument shaft 120 resides in trough 222. Instrument shaft 120 mayalso couple to a roll actuation mechanism (not shown), which may bemounted in an instrument backend as described in co-filed U.S. Pat. App.No. 62/362,340 (filed Jul. 14, 2016), entitled “GEARED ROLL DRIVE FORMEDICAL INSTRUMENT.” Drive elements 240, which may pass through fluidtrough 222 and extend through instrument shaft 120 to a distal tool, maysimilarly have proximal ends connect to actuation mechanisms provided inan instrument backend as disclosed in co-filed U.S. Pat. App. No.62/362,431 (filed Jul. 14, 2016), entitled “MULTI-CABLE MEDICALINSTRUMENT.” Drive elements 240 also pass through a cap 230 for trough222. As described further, cap 230 may incorporate a guide for driveelements 240, and the cap and guide system may create a close fit todrive elements 240 to reduce of minimize loss of cleaning fluid throughflush cap 230. Some cleaning fluid may leak through cap 230 into piece210, but the housing comprising piece 210 is not required to be watertight, and any cleaning fluid that leaks around flush cap 230 may drainout through gaps, for example, between separate chassis or housingpieces, around input spindles 141 to 146 or through other openings 119in backend 130 as shown in FIGS. 1A and 1B. An additional inlet 218 mayallow secondary flushing of the backend 130 of any contaminants that maybe back-washed from shaft 120 into the housing comprising piece 210 orintroduced during handling of the instrument.

FIG. 3A shows a partial cutaway view of a portion of the medicalinstrument of FIG. 2 when assembled. As shown, piece 210 includes inlet150, which may include a female Luer port fitting and which terminatesprotrusion 212. Protrusion 212 may include a cone-shaped protrusion thatfits snuggly into piece 220. Piece 210 may thus direct fluid into trough222. Trough 222 in piece 220 in turn directs fluid for a short distancealong the perimeter of the medical instrument to the location of theproximal end of instrument shaft 120.

Flush cap 230 fits in trough 222 to enclose a fluid channel from inlet150 to the proximal end of instrument shaft 120. Flush cap 230 may havethin walls of a material that flex to allow a tight fit into piece 220.For example, flush cap 230 may be made of plastic. Cap 230 in oneimplementation is made of about 10 percent polytetrafluoroethylene(PTFE) to reduce friction against the driving elements, particularlygrip drive rod 244, and the remaining 90 percent of cap 230 may bepolyether imide (PEI), although other high temperature plastics wouldalso be suitable. The thin walls of cap 230 may also press against thewalls of trough 222 so that fluid pressure in the fluid channel has atendency to tighten the seal of cap 230 against piece 220 and therebyresist or prevent fluid from leaking out around the edges of cap 230. Afurther chassis piece 350, which fits onto piece 220, may also captureflush cap 230 to keep fluid pressure or vibrations from pushing cap 230out of place.

Holes 232 (also called “openings”) in flush cap 230 as shown in FIG. 3Ballow drive elements 240, such as drive cables 242 and a push-pull rod244, to pass through cap 230. Drive elements 240 further extend throughtrough 222 and into instrument shaft 120. Cap 230 may be used with acable guide 330 that supports the load that results from redirectingdrive elements 240 from a path exiting instrument shaft 120 to a pathtowards drive mechanisms in the backend of the medical instrument. Cableguide 330 may be made of a resilient and durable material such as metalthat will not be quickly eroded by the back-and-forth sliding of driveelements 240 against cable guide 330. For example, cable guide 330 maybe made of hardened stainless steel and may support drive cables made oftungsten. In contrast, flush cap 230 may be made of a flexible materialthat may provide lower costs and a better seal against piece 220. AnO-ring 320 may act as a spring to push cable guide 330 against flush cap230.

A roll gear 310 as shown in FIG. 3A is coupled to instrument shaft 120and may transmit rotation from a roll actuation mechanism to instrumentshaft 120. The shape of the proximal end of roll gear 310, and thesmallness of the gap between roll gear 310 and piece 220 may be used todirect most of the cleaning fluid from fluid trough 222 into instrumentshaft 120 instead of out of the medical instrument through the gap tothe outside of roll gear 310 and instrument shaft 120. Further,instrument shaft 120 may fit snugly inside roll gear 310 to similarlyprevent leakage between instrument shaft 120 and roll gear 310. Proximaland distal roll bearings 312 and 314 support axial and radial loads oninstrument shaft 120 and provide further sealing against leakage ofcleaning fluid during a cleaning process. In particular, roll gear 310may couple to instrument shaft 120 using gaps in roll gear 310 that maybe mated to tabs on instrument shaft 120, and bearings 312 or 314 maycover such gaps so that the cleaning fluid stays inside instrument shaft120.

FIGS. 3A and 3B show an implementation of a medical instrument in whichpush-pull rod 244 extends through center holes in flush cap 230 andcable guide 330, and drive cables 242 extend through separate holes inflush cap 230 and separate notches around the perimeter of the centerhole in cable guide 330. In accordance with an aspect disclosed herein,flush cap 230 and cable guide 330 may be shaped to overlap and provide aclose fit to drive cables 242. FIG. 4A, for example, shows a bottom viewof one possible implementation of cable guide 330. In the implementationof FIG. 4A, cable guide 330 has U-shaped notches 332 around theperimeter of a central hole 334, and U-shaped notches 332 may be sizedto closely fit respective cables 242. Further, each cable 242 may havean end 442 (which may comprise a crimp) with a diameter larger thanU-shaped notches 332. Each end 442 may, for example, be used to connecta drive cable to an actuation mechanism, e.g., an input spindle. Cap 230may have teardrop-shaped holes 232 as shown in FIG. 4B. In particular,an outer edge of each hole 232 may have a diameter large enough forthreading of an end 442 of a cable 242 through the hole 232, and aninner edge of each hole 232 may be sized to snuggly fit a cable 242.When cable guide 330 is pushed up against flush cap 230, the overlap ofholes 232 in cap 230 with corresponding U-shaped notches 332 createsthrough holes 432 that snuggly fit around cables 242 as shown in FIG.4C. Through holes 432 may particularly be smaller than crimp or end 442of a drive cable 242 but big enough to accommodate cable 242. Theteardrop-shaped holes 232 in flush cap 230 may be oriented, shaped, anddrafted or tapered so that the drive cables 242 touch only the metal ofcable guide 330, so that flush cap 230 may be made of plastic or otherrelatively soft material and still will not wear away or decrease theamount of sealing during use. The central hole 234 in flush cap 230 maybe similarly close fit to push-pull rod 244, so that the combination ofcap 230 and cable guide 330 provides close fits around drive cables 242and push pull rod 244, which inhibits leakage of cleaning fluid into thebackend of the instrument. Push-pull rod 244 may follow a bend ininstrument shaft 120, so that flush cap 230 may support a small radialload. Flush cap 230 may however be made of plastic as described aboveand may still support grip rod 244 with low friction, avoiding theproblem of wear. After assembly, the close fit around drive cables 242and drive rod 244 creates a path with high resistance to leakage andthat directs most of the cleaning fluid down the instrument shaftinstead of into the backend of the instrument. A complete seal is notnecessary as long as a substantial portion of the water or othercleaning fluid is directed down the instrument shaft.

Assembly of the instrument using flush cap 230 and cable guide 330 canthread the larger end 442 of each drive cable 242 through central hole334 in cable guide 330, before the cable 242 is seated in a U-shapednotch 332. Ends 442 may be similarly threaded through the larger outportions of holes 232 in cap 230, before cable guide 330 shifts cables242 toward the smaller inner portions of holes 232 when cable guide 330is pushed against cap 230. The two-piece cap structure thus enablespre-crimped cables to be passed through flush cap 230, which removes theneed to crimp drive cables 242 on the assembly line after the drivecables 242 have been threaded through portions of a medical instrumentbeing manufactured.

FIG. 4B also illustrates how cap 230 may include additional holes 236for electrical lines, e.g., for a medical instrument that performscauterization. As shown in FIG. 4C, cable guide 330 may omit holes forelectrical lines when a medical instrument does not require anelectrical connection to the distal tool, and cable guide 330 may sealholes 236 when cable guide is pressed against the underside of cap 230.

Returning to FIGS. 3A and 3B, O-ring 320 may be compressed between cableguide 330 and chassis piece 220 and therefore may push cable guide 330up against the inside surface of flush cap 230. The bottom of cableguide 330 may include legs 338 that contact O-ring 320, so that gapsbetween legs 338 on cable guide 330 provide openings through whichcleaning fluid passes to enter instrument shaft 120 during a flush orcleaning process. In an alternative implementation, O-ring 320 may bereplaced with a spring or even a rigid surface/spacer that similarlypushes cable guide 330 against flush cap 230 and leaves openings forfluid flow into instrument shaft 120.

FIG. 4A as described above shows a cable guide 330 for a medicalinstrument that is a non-energized instrument, e.g., a medicalinstrument that does not require electrical lines extending through theinstrument shaft. Accordingly, cable guide 330 of FIG. 4A has no holesfor electrical wires and covers up holes 236 in flush cap 230 so wateror other cleaning fluid does not get through holes 236 during a flushprocess.

A medical instrument capable of monopolar cautery may electricallyenergize push-pull rod 244, so that push-pull rod 244 is used for bothgrip actuation and to conduct electrical power to jaws of the distaltool. A monopolar cautery instrument may, however, use electrical linesfor electrical shielding of the instrument shaft. FIG. 5A, for example,shows a cable guide 530 having two pins 540 electrically coupled tocable guide 530. Pins 540 may be sized to fit through holes 236 and toclose off holes 236 in flush cap 230 in order to block leakage of wateror other cleaning fluid. As shown in FIG. 5B, shield wires 520 may beconnected to pins 540 to ground metal cable guide 530, which whenassembled in a medical instrument may be electrically connected toinstrument shaft 120 and drive cables 242. Electrical shield wires 520may alternatively be connected to cable guide 530 using othertechniques, e.g., wires 520 may be crimped or soldered directly to cableguide 530 instead of using pins 540. Flush cap 230, which may be made ofan electrically insulating plastic as described above, may include guidehole 234 for push-pull rod 244 so that push-pull rod 244 is electricallyinsulated from metal cable guide 530.

A bipolar cautery instrument may employ electrical lines running throughthe instrument shaft alongside the drive cables. A cable guide 630 asshown in FIG. 6A may include two holes 640 for insulated wires or otherelectrically conductive lines 620 as shown in FIG. 6B to pass through enroute to the distal tool. Insulated conductors 620 may substantiallyfill holes 640 in cable guide 630 or holes 236 in cap 230 so that wateror other cleaning fluid will be directed away from cable guide 630 andmostly down the instrument shaft as in other implementations describedabove.

Some implementations of flush systems disclosed herein may provideseveral advantages over alternative flush systems. In particular, someflush systems disclosed herein do not require a flush tube extendingthrough an instrument shaft and therefore may provide a more compactflush system that works in narrower instrument shafts and may provide aflush system that avoid problems that may arise when a flush tubebecomes kinked. Further, implementations using a two-piece flush cap cancomplete a “seal” (not necessarily a perfect seal, but any leakage is atan acceptable amount) around each drive cable and still enable use ofpre-crimped cables, which may simplify assembly of a medical instrument.Some implementations can direct cleaning fluid along a path of leastresistance down the instrument shaft without requiring or using fullseals on drive elements, which may avoid problems associated with sealsthat wear away quickly from the sawing action of the drive cables.Further, a flush path may be implemented with thin walled componentsmating together such that water or cleaning fluid pressure tends toincrease the amount of sealing, which may improve reliability ofcleaning a medical instrument.

Although particular implementations have been disclosed, theseimplementations are only examples and should not be taken aslimitations. Various adaptations and combinations of features of theimplementations disclosed are within the scope of the following claims.

1. A medical instrument comprising: a shaft having one or more exitholes near a distal end of the shaft; a tool coupled to the distal endof the shaft; and a backend including: a mechanism that manipulates adrive element that extends through the shaft and couples to the tool, afluid inlet, and a fluid channel assembly in communication with thefluid inlet and containing a proximal end of the shaft.
 2. The medicalinstrument of claim 1, wherein: the fluid channel assembly comprises acap adjacent to the proximal end of the shaft; and the drive elementextends through the cap and into the shaft.
 3. The medical instrument ofclaim 2, further comprising: a chassis comprising the fluid inlet, thechassis further comprising a trough with sidewalls extending from asurface of the chassis for securing the cap to the chassis.
 4. Themedical instrument of claim 3, wherein the cap comprises a flexibleportion that seals against the sidewalls of the trough.
 5. The medicalinstrument of claim 2, further comprising: a guide secured on the cap;wherein the guide comprises a resilient surface that redirects the driveelement.
 6. The medical instrument of claim 5, wherein: the capcomprises a first opening; the guide comprises a second opening; and thefirst opening and the second opening overlap to create a through holethat is smaller than the first opening, that is smaller than the secondopening, and that closely fits around the drive element.
 7. The medicalinstrument of claim 6, wherein: the drive element comprises a cable anda crimp on the cable; and the crimp fits through the first opening andthrough the second opening and does not fit through the through hole. 8.The medical instrument of claim 1, wherein: the tool further comprisesone or more vents configured for fluid flow.
 9. The medical instrumentof claim 8, wherein the one or more vents expose the drive element tocleaning from outside the shaft.
 10. A method for cleaning a medicalinstrument, comprising: receiving a cleaning fluid into a fluid channelassembly, the fluid channel assembly containing a proximal end of ashaft of the medical instrument, wherein a drive element extends throughthe fluid channel assembly and through the shaft, and the drive elementcouples to a tool at a distal end of the shaft; removing contaminantsfrom inside the shaft by guiding the cleaning fluid to flow through theshaft in a proximal-to-distal direction; and draining of the receivedcleaning fluid out of the shaft through one or more exit holes near thedistal end of the shaft.
 11. The method of claim 10, further comprising:employing a cap adjacent to the proximal end of the shaft to direct thecleaning fluid into the shaft; wherein the drive element extends throughthe cap and into the shaft.
 12. The method of claim 11, wherein the capfits closely around the drive element and resists flow of the cleaningfluid out of the fluid channel assembly, except through the shaft. 13.The medical instrument of claim 2, wherein the cap comprises a pluralityof teardrop-shaped holes.
 14. The medical instrument of claim 1, whereinthe fluid channel assembly comprises a cap enclosing at least a portionof a fluid channel between the fluid inlet and the proximal end of theshaft.
 15. The medical instrument of claim 14, wherein the cap isplastic.
 16. The medical instrument of claim 15, wherein the plasticcomprises polytetrafluoroethylene (PTFE) and polyether imide (PEI). 17.A medical instrument, comprising: a shaft comprising a proximal portionand a distal portion, one or more exit holes being defined in the distalportion of the shaft; a housing supporting the proximal portion of theshaft, the housing comprising a fluid inlet and a trough; and a capcoupled to the trough to enclose a fluid channel between the fluid inletand the proximal portion of the shaft; and a cleaning channel definedfrom the inlet port, through the fluid channel, through the shaft, tothe one or more exit holes.
 18. The medical instrument of claim 17,wherein: one or more holes are defined in the cap; and the medicalinstrument comprises a drive element that extends through the shaft andthrough the one or more holes defined in the cap.
 19. The medicalinstrument of claim 17, further comprising a guide, wherein: a firstopening is defined in the cap; a second opening is defined in the guide;and the first opening and the second opening overlap to create a throughhole between the cap and the guide, the through hole being smaller thanthe first opening and the second opening.
 20. The medical instrument ofclaim 17, wherein: the trough comprises opposing sidewalls; and the capcomprises a flexible portion that seals against the sidewalls of thetrough.